H. Harvey Michels

Theoretical studies of spin‐forbidden radiationless decay in polyatomic systems. II. Radiationless decay of a‐N2O2

The stability with respect to spin‐forbidden radiationless decay of the previously reported [J. Chem. Phys. 88, 7248 (1988)] asymmetric dimer of NO, N–N–O–O (a‐N2O2) is considered. The spin‐allowed decay channel a‐N2O2(1A’)→N2O(X 1Σ+)+O(1D) is endoergic. However, the spin‐forbidden decay channel a‐N2O2(1A’)→N2O(X 1Σ+)+O(3P) is exoergic. Large scale multireference configuration interaction wave functions, approximately 300 000–1 400 000 configuration state functions, based on double zeta polarization and triplet zeta polarization bases are used to study this process. The minimum energy crossing of the ground singlet 1A’ state and the lowest excited triplet 3A‘ state was determined as was the interstate spin–orbit coupling. This electronic structure data was used in the context of a simple one‐dimensional model to show that a‐N2O2 is rapidly predissociated to N2O(X 1Σ+) and O(3P).

Rotational Spectrum, Tunneling Motions, and Potential Barriers of Benzyl Alcohol

The rotational spectra of benzyl alcohol and of its OD isotopologue have been assigned and measured in a supersonic expansion, either with pulsed-jet Fourier transform microwave or free jet absorption millimeter wave spectroscopy. The spectrum is consistent with a gauche conformation of the oxygen atom, characterized by a theta (OC(7)-C(1)C(2)) dihedral angle of approximately 55 degrees. Such a configuration is 4-fold degenerate, corresponding to minima with theta approximately +/-60 degrees, +/-120 degrees. The four equivalent minima are separated by two kinds of barrier, corresponding to theta = +/-90 degrees, and 0 or 180 degrees. Only the theta = +/-90 degrees barriers are low enough to generate a tunneling splitting, which has been measured in a spectrum strongly perturbed by tunneling interactions. The observed splittings diminish considerably upon deuterium substitution. The tunneling splittings are consistent with a barrier about 280 cm(-1) and high level ab initio calculations predicting a 320 cm(-1) barrier.

The electronic structure and stability of NF5 and PF5

An ab initio study of the electronic structure of NF5 and PF5 has been carried out using Mo/ller–Plesset perturbation theory. Optimized geometries were calculated at the SCF and MP2 levels of theory using several basis sets, ranging from 6‐31G to 6‐311G(2df). A vibrational analysis indicates that NF5, in D3h symmetry, has all real frequencies, even if d orbital contributions are set to zero. Dissimilar N–F bond lengths (req=1.38 A, rax=1.58 A) are found, in contrast to PF5, which exhibits nearly equal equatorial and axial bond lengths. A topological analysis of the calculated charge distribution in NF5 indicates true pentavalent coordination. Spectroscopic data for NF5 have been calculated using a scaled MP2 force field based on the known NF3 molecule. A comparison of calculated thermochemistry between NF3 and NF5 yields a predicted standard state heat of formation for NF5(g) of ΔH0f (0 K)=+25.1 kJ/mol. Our results suggest that synthesis of NF5 and other hypervalent compounds of first row atoms may be pos...

Structure and stability of trinitramide

Ab initio calculations of the structure and thermochemistry of trinitramide, N(NO 2 ) 3 , are reported. A vibrationally stable C 3 structure having 1.545 A N-N bond lengths is found at the MP2/6-31 G * level of theory. The heat of formation of trinitramide is estimated to be 59 kcal/mol. Thermal decomposition of trinitramide most likely occurs via N-N bond cleavage, which is estimated to require 26 kcal/mol

Long range intermolecular interactions between the alkali diatomics Na2, K2, and NaK

Long range interactions between the ground state alkali diatomics Na(2)-Na(2), K(2)-K(2), Na(2)-K(2), and NaK-NaK are examined. Interaction energies are first determined from ab initio calculations at the coupled-cluster with singles, doubles, and perturbative triples [CCSD(T)] level of theory, including counterpoise corrections. Long range energies calculated from diatomic molecular properties (polarizabilities and dipole and quadrupole moments) are then compared with the ab initio energies. A simple asymptotic model potential E(LR)=E(elec)+E(disp)+E(ind) is shown to accurately represent the intermolecular interactions for these systems at long range.

Ab initio potential curves for the X2Σu+, A2Πu and B2Σg+ states of Ca2+

We report \textit{ab initio} calculations of the X

Potential energy surface of the 12A′ Li2 + Li doublet ground state

^2 \Sigma_{u}^+

Ab initio potential curves for the X

, A

^2\Sigma_u^+

^2\Pi_u

, A

and B